The present invention relates to improvements in surgical electrodes, especially in so-called temporary leads for cardiac pacing and monitoring purposes.
U.S. Pat. No. 4,010,756 discloses a heart pacer lead wire wherein the distal end of a conductor is connected with a separable needle serving to implant the pole of the conductor in the heart wall. The proximal end of the conductor extends through and outwardly from the thorax for attachment to a pacemaker. The conductor includes several strands of very thin stainless steel wire surrounded by a sheath consisting of synthetic plastic material which is not likely to be rejected by the body of the patient. The two end portions of the conductor are bare and the length of each of the bare end portions is in the range of 2 cm. The surgical needle (preferably a curved needle) is integral with but can be broken or severed away from the bare end portion at the distal end; the needle serves to implant the bare end portion (pole) at the distal end of the conductor into the myocardium and is thereupon separated from the distal end and removed from the body. The other bare end portion is at first secured to a straight surgical needle which is caused to penetrate through the thorax and establishes the electrical connection between the implanted pole and a pacemaker. This enables the latter to stimulate the heart in the event of disturbances of the rhythm. A second electrode is implanted in a similar manner to locate a second pole in the myocardium. The electrodes remain implanted for a period of two to three weeks and are thereupon extracted from the body.
A drawback of the just described and similar electrodes is that each pacing or monitoring operation necessitates the implantation of two discrete electrodes, i.e., the implantation of two discrete conductors by means of two discrete needles. Thus, the implantation of two electrodes (namely the introduction of two poles into the heart wall) necessitates the making of two punctures in the heart wall. This greatly increases the likelihood of accidental premature extraction of the one or the other electrode and renders it necessary to forestall such possibility by appropriate surgical undertakings. For example, the distal ends of the electrodes are slightly bent or a slight ligature is placed around each of the electrodes. It was also proposed to provide the distal ends of such electrodes with loops to facilitate their anchoring in the heart wall. All such undertakings are time-consuming, costly and necessitate additional penetration into the tissue of the heart.
Applicants are further aware of German Utility Model No. 70 47 748 which discloses a bipolar electrode for intravenous introduction into a cardiac cavity, of German Offenlegungsschrift No. 1,939,806 which discloses two unipolar electrodes and discrete needles, of German Offenlegungsschrift No. 28 46 136 which discloses a unipolar electrode, and of published European patent application No. 0 083 674 which discloses a unipolar electrode with a curved surgical needle.